Machines, such as earthmoving and construction machines, generally include an engine that powers some type of hydraulic system. The hydraulic system may provide functionality and control to various aspects of the machines. For example, some machines employ a hydraulic system for propelling the machine and/or providing hydraulic power to work implements of the machine, such as linkages, buckets, shovels, and other tools. The hydraulic system may typically include one or more pumps used to convert mechanical power from the engine into hydraulic power.
The pump may be connected to a hydraulic actuator and may provide pressurized fluid to one or more fluid chambers of the hydraulic actuator. Hydraulic actuators, such as pistons/cylinders and fluid motors, are commonly used to move the work implements. More specifically, each hydraulic actuator typically includes at least two fluid chambers that are disposed on opposite sides of a movable element. The movable element is, in turn, connected to the work implement. These hydraulic systems may include an electrohydraulic valve arrangement that selectively connects the pump with one of the fluid chambers of the hydraulic actuator.
For instance, to move the work implement in a certain direction, the electrohydraulic valve arrangement is controlled so that pressurized fluid is provided to one chamber of the hydraulic actuator at the same time fluid is allowed to flow out of the other chamber. This creates a pressure differential over the movable element of the hydraulic actuator. When the force exerted on the movable element is greater enough to overcome the resistant force of the work implement, the movable element will move towards the area of lower fluid pressure existing in the opposite chamber of the hydraulic actuator, thereby moving the work implement. A control lever, or other type of operator control, may govern the motion of the work implement.
However, a cost of the electrohydraulic valve arrangement may be expensive with complex systems requiring numerous pieces of hardware.
A hydraulic system and method are disclosed in U.S. Pat. No. 9,194,107, entitled, “Regenerative Hydraulic Systems and Methods of Use.” In the '107 patent, the hydraulic systems are capable of controlling the operation of multiple actuators, particular examples of which are linear and rotary actuators. The '107 systems contain distributed valves systems and one or more positive displacement units having both pumping and motoring modes. In particular, the '107 systems enable valves and actuators within the systems to reconfigure themselves so that flow from assistive loads on one or more actuators can be used to move one or more other actuators subjected to a resistive load.
While arguably effective, there is still a need for a hydraulic system with a cost-effective electrohydraulic valve arrangement that provides independent metering.